Compliant framework and methods of use

ABSTRACT

An expansion mechanism that includes an elongate instrument and a plurality of struts arranged around the elongate instrument provides radial expansion of a medical device. Each strut has a first end pivotally connected to the elongate instrument and a second strut that expands radially outward. Each strut further carries a flexible line which has a proximal end and a distal end. The distal end of each line passes beyond the second end of the strut which carries it and is attached to the strut immediately adjacent the strut which carries it. Methods of using such an expansion mechanism are also disclosed, particularly to provide deployment of medical devices within a patient&#39;s blood vascular system.

[0001] This application is a continuation of U.S. application Ser. No.10/043,869, filed Nov. 1, 2001, now U.S. Pat. No. 6,500,191, which is acontinuation of U.S. application Ser. No. 09/568,532, filed May 9, 2000,which is a continuation of U.S. application Ser. No. 09/199,232, filedNov. 24, 1998, now U.S. Pat. No. 6,083,239, all of which are expresslyincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to an expansion mechanism forradial expansion of a medical device. More particularly, the inventionrelates to a compliant framework which conforms to the interior anatomyof a patients, e.g., interior blood vessel wall, with minimum gap. Theframework provides structure for medical devices such as filter meshes,damming or occlusion methods, flow direction devices, and locating andmeasuring applications.

BACKGROUND OF THE INVENTION

[0003] During open heart surgeries, such as coronary artery bypassgraft, valve repair surgeries, thoracic aneurysm repair, removal ofatrial myxoma, and septal defect repairs, currently the most commonmethod of temporarily occluding the ascending aorta utilizes amechanical cross clamp. Aortic occlusion is needed to establishisolation of coronary circulation from the peripheral circulatory systemduring cardiac arrest, so that peripheral organs would not be paralyzedby cardioplegic solution. An arterial cannula is commonly inserted in apatient's aorta or femoral artery to provide return of oxygenated bloodfrom a bypass-oxygenator machine, whereas a venous catheter is insertedinto the right atrium, superior vena cava, or inferior vena cava tocarry deoxygenated blood from the heart to a bypass-oxygenator machine.Other less common means of occluding the aorta include percutaneousballoon catheter occlusion, direct aortic balloon catheter (Foley)occlusion, aortic balloon occluder cannula, and an inflating diaphragmoccluder (Hill-occlusion trocar).

[0004] Manipulation of ascending aorta during mechanical cross-clampingor other means of aortic occlusion often dislodges atheromatous plaguesfrom the ascending aorta downstream to peripheral organs. Tissue debris,air, or calcium plaques may also arise from cardiac manipulation.Embolization of atheromatous plaques, tissue debris, or calcium plaquesmay lead to stroke, organ death or ischemia.

[0005] Devices for filtering blood have been designed to reduce apatient's peri-operative risk of peripheral embolization, therebyreducing surgical morbidity and mortality. The vast majority of thesedevices are designed for permanent placement in veins, in order to trapemboli destined for the lungs, e.g., Kimmell, Jr., U.S. Pat. No.3,952,747, Cottenceau et al., U.S. Pat. No. 5,375,612, Gunther et al.,U.S. Pat. No. 5,329,942, and Lefebvre, French Pat. No. 2,567,405,incorporated herein by reference. Few intravascular devices are designedfor arterial use, e.g., Ginsburg, U.S. Pat. No. 4,873,978, Ing. WalterHengst GmbH & Co, German Pat. DE 34 17 738, da Silva, Brazil Pat.Application No. P19301980A, and Barbut et al, U.S. Pat. No. 5,769,816,all incorporated herein by reference, have been developed to entraparterial emboli during open-heart procedures.

[0006] The aforementioned devices all have drawbacks in that a filter ormembrane to entrap emboli is deployed by means of an umbrella mechanism,thereby failing to accurately follow the rough non-uniform contour ofthe internal blood vessel wall. A built-in spring offers the force tobring the frame into contact with the vessel wall. The umbrella frame,however, would segment the contact, thereby only assuring a seal at eachdiscrete arm in contact. Moreover, in using the current filter devices,an operator has little or no feel for contact between the filtermechanism and the vessel wall. Further, current designs do not permitclosure which is sufficiently tight and secure to prevent release ofentrapped emboli.

[0007] A need exists for devices and methods which provide contact ofmedical devices and vessel walls with minimum gap, give an operator afeel for the vessel wall during deployment, and permit efficient andsecure closure to ensure retention of entrapped debris.

SUMMARY OF THE INVENTION

[0008] The present invention relates to an expansion mechanism forradial expansion of a medical device. More particularly, the inventionprovides a compliant framework which conforms to a patient's interioranatomy (such as a vessel wall) with minimum gap, provides structure forfilter meshes, damming or occlusion devices, flow direction devices,locating and measuring applications, and provides a feel for the contourof vessel wall during deployment. The framework may be a metal, plastic,gel or foam.

[0009] In one embodiment, the device includes an elongate instrumentwhich may comprise a cannula. A plurality of struts are arrangedcircumferentially around the elongate instrument. Each strut has twoends. The first end is pivotally connected to the elongate instrumentwhile the second end expands radially outward. Each strut carries a wireor line having a proximal end and a distal end. The distal end of theline passes beyond the second end of the strut which carries it. Thedistal end of each line is attached to the strut immediately adjacent tothe strut which carries it. In one embodiment, the framework has twostruts and two lines. In other embodiments, the framework may havethree, four, five, or six struts, and an equal number of lines arrangedaround the elongate instrument.

[0010] In another embodiment, the struts are mounted on a distal end ofa cannula. Each strut may comprise a tubular member having a lumen andeach flexible line is carried by the lumen of each tubular strut. Thesecond end of each strut may curve toward the immediately adjacentstrut.

[0011] In another embodiment, the expansion framework may be equippedwith a filter mesh having two edges. A first edge of the mesh attachescircumferentially and continuously about the elongate instrument and isaligned with the first end of each strut. A second edge of the mesh mayattach circumferentially to the second end of each strut and/or to asegment of each line which extends beyond the second end of each strut.The elongate instrument may comprise a blood filtration cannula. Whenthe filter mesh is deployed inside a patient's blood vessel, as thesecond end of each strut expands radially outward, and the filter meshalso expands radially outward to contact the vessel wall. After embolicmaterials are collected from the blood onto the filter mesh, the meshand struts are collapsed, and the cannula is removed.

[0012] In an alternative embodiment, the elongate instrument comprises apercutaneous catheter. The catheter may include a balloon occluder. Theballoon occluder may be mounted proximal the struts. This embodimentprovides occlusion of the blood vessel, such as aortic occlusion in openheart procedures (e.g., valve repair), in addition to providing anexpansion mechanism for a filter or other medical devices. Using thisconstruction the filter is disposed between the occluder and the heartand captures debris (which accumulates in the heart and aortic rootduring bypass) when the heart resumes beating and the occluder isremoved. For an extensive discussion of the use of percutaneousfiltration catheters of this type for prevention of stoke followingvalve repair surgery, the reader is referred to Jang, U.S. applicationSer. No. 09/170,359, filed Oct. 13, 1998, which is incorporated hereinby reference.

[0013] The methods of the present invention include deployment andexpanding a portion of a medical device within a patient by using theexpansion mechanism as described above. A medical device is insertedinto the patient through an incision. The flexible lines are pusheddistally by an operator to pay out a portion of each line beyond the endof each strut, to thereby expand the strutted portion of the deviceradially outward. By manipulating the lines, the operator is able tofeel for the contour of an interior vessel wall, thereby minimizing thegap between the medical device and the vessel wall. To remove themedical device, the flexible lines are pulled proximally to contract thestrutted portion of the device radially inward, and the device isremoved from the patient.

[0014] In a preferred method, a cannula is equipped with a filter meshdisposed over the struts, and the filter mesh is expanded by pushing theflexible lines distally. During cardiac surgeries, such as valve repairsurgery, the filter mesh captures embolic materials which are releasedfrom the heart or aorta. During carotid endarterectomy, the filter meshentraps calcium and atheromatous debris from the carotid artery. After asurgical procedure is accomplished, the flexible lines are pulled andthe filter mesh is contracted tightly against the elongate element. Inthis method, the trapped emboli are secured by the tight compliantframework during removal.

[0015] It will be understood that there are several advantages in usingthe framework described above. For example, (1) the filter frame andchassis allow for perfusion of fluid or blood through the center of theexpansion mechanism; (2) trapped emboli are secured within a filter meshwhen the wire frame is drawn closed and tight; (3) the expansionmechanism provides an operator feedback of contact between the devicesand vascular wall; (4) a filter expansion mechanism may be combined witha balloon occluder and/or “direct stick” access device; and (5) theframework can adjust to a wide range of blood vessel diameter.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 depicts an embodiment of an expansion mechanism accordingto the invention having its struts expanded radially outward.

[0017]FIG. 2 depicts one embodiment of a cannula having a filter mountedon its expansion framework according to the invention.

[0018]FIG. 3 depicts an aorta having the filter of FIG. 4 deployed abovethe aortic root.

[0019]FIG. 4 depicts an alternative embodiment of the cannula withfilter in FIG. 4 deployed above the aortic root.

[0020]FIG. 5 depicts an embodiment of an expansion mechanism accordingto the invention having its struts and flexible lines pulled tightagainst an elongate instrument.

[0021]FIG. 6 depicts a frontal view of the expanded mechanism shown inFIG. 1.

[0022]FIG. 7 depicts one embodiment of a percutaneous catheter having afilter mounted on its expansion framework according to the invention.

[0023]FIG. 8 depicts an alternative embodiment of a percutaneouscatheter having a filter and a balloon occluder.

[0024]FIG. 9 depicts different entry sites for the percutaneous cathetershown in FIG. 7.

DETAILED DESCRIPTION

[0025] The expansion mechanism is best employed in a vessel, such as anartery, e.g., a patient's aorta, for providing deployment of medicaldevices which require close approximation of the devices and the aorticwall. However, the expansion mechanism may also be suitable fordeployment of medical devices such as damming or occlusion devices, andlocating and measuring applications in a patient's veins or bodycavities.

[0026] An embodiment of the framework is depicted in FIG. 1. Thisembodiment comprises struts 2, 8, and 10, each arrangedcircumferentially around elongate cannula 1. Other embodiments maycomprise 3, 4, 5, 6, 7 or more struts. Each strut has first end 3 andsecond end 4. The first end is pivotally connected to cannula 1, whereasthe second end expands radially outward. Flexible line 5, havingproximal end 7 and distal end 6, is carried by each strut. End 6 of eachline passes beyond second end 4 of each strut which carries it. End 6 isattached to the strut immediately adjacent the strut which carries it.For example, the distal end of flexible line 5, which passes beyond end4 of strut 2, is attached to end 4 of strut 8.

[0027] In use, a medical device is operated by actuation of theframework. For example, when filter devices are needed, an expandablefilter mesh is disposed about the framework as depicted in FIG. 2.Cannula 1 may be a blood filtration cannula having proximal end 23,distal end 22, and lumen 20 in between. Proximal end 23 may be adaptedfor attachment to a bypass-oxygenator machine. The struts are shownmounted on the distal end of the cannula. A first edge of mesh 30 isattached circumferentially about cannula 1 and aligned with end 3 ofeach strut, and a second edge of mesh 30 is attached circumferentiallyto a segment of line 6. Flexible lines 5 may be carried by additionallumen 26. In this embodiment, the cannula includes balloon occluder 45which is mounted distal to the struts and in communication with ballooninflation lumen 46.

[0028] When the cannula of FIG. 2 is used for aortic cannulation duringcardiothoracic surgeries, such as coronary artery bypass, heart valverepair, septal defect repair, resection of atrial myxoma, and thoracicaneurysm repair, the cannula is inserted into a patient's ascendingaorta through an open chest incision. In minimally invasive procedures,the cannula is inserted into the aorta through a port access on thepatient's chest wall. After the cannula is positioned within the aortaas depicted in FIG. 3, balloon occluder 45 is inflated to isolate thecoronary circulation from the peripheral circulation. The flexible linesor wires are pushed distally to expand the mesh radially outward so thatthe first edge of the filter mesh is in close contact with the inneraortic wall. An operator can manipulate the flexible lines to optimallyposition the mesh in the aorta with minimum gap. In this embodiment,oxygenated blood may be perfused from a bypass-oxygenator through lumen20 and distal end 22 downstream to the aorta during cardiopulmonarybypass.

[0029] An alternative embodiment of a blood filtration cannula accordingto the present invention is depicted in FIG. 4. Cannula 1 has proximalend 46, which is adapted for attachment to a bypass-oxygenator machine,distal end 22 and lumen 20. The cannula is shown inserted into theascending aorta directed upstream in the aorta in contrast to thecannula depicted in FIG. 3, which is inserted downstream in the aorta.Balloon occluder 45 is mounted proximal to the expansion framework.Filter mesh 30 is mounted on the framework. In use, the balloon occluderis inflated through inflation lumen 46 to provide circulatory isolation,and the filter mesh is expanded to contact the interior aortic wall bypushing on flexible lines or wires. Oxygenated blood can be perfusedthrough lumen 20 and port 21 downstream into the aorta to provideoxygenation to peripheral organs during cardiopulmonary bypass.

[0030] After a surgeon has performed surgery on the heart, the balloonoccluder may be deflated. The lines are pulled to contract the mesh.Distal ends 6 of flexible lines 5 and struts 2 can be drawn closedtightly against cannula 1 as depicted in FIG. 5. In this way, thetrapped embolic material is secured in the tightly contracted filtermesh, thereby avoiding unintended release during removal of theframework and mesh.

[0031]FIG. 6 depicts a frontal view of an expansion mechanism. Struts 2are expanded radially outward from cannula 1 by pushing flexible lines 5distally. Distal ends 6 of flexible lines 5 pass through end 4 of eachstrut and are attached to the strut immediately adjacent the strut whichcarries it.

[0032]FIG. 7 depicts an embodiment of a percutaneous catheter having afilter according to the present invention. Catheter 1 has the expansionframework mounted on distal end 22. Filter mesh is mounted struts 2 ofthe framework. Flexible lines 5 may be carried in lumen 20 of thecatheter.

[0033] In certain embodiments of the percutaneous catheter depicted inFIG. 7, the catheter may further include a balloon occluder. In FIG. 8,distal end 22 of catheter 1 has filter mesh 30 mounted on struts 2 ofthe framework. The struts are operated by flexible lines 5 outside thecatheter. Balloon occluder 45 is mounted proximal to the framework andcommunicates with inflation lumen 46. In other embodiments (not shown),the balloon occluder is mounted distal to the framework.

[0034] In use, the percutaneous catheter may be inserted through variouscutaneous puncture sites to position above the aortic root to entraptissue debris, calcium, and thrombi during heart valve repair surgeries.FIG. 9 depicts the percutaneous catheter of FIG. 7 entering thepatient's left femoral artery and traversing the left iliac artery,descending aorta, and aortic arch to reach the ascending aorta. Thedistal end of the catheter is generally positioned about 4 centimetersabove the aortic valves. Alternatively, the catheter can be insertedthrough the brachial arteries, especially in patients whose femoralarteries are not suitable for puncture. In elderly patients, the femoralarteries are often diseased, damaged or thrombosed. Catheter 1 is shownentering through the right brachial artery.

[0035]FIG. 9 also depicts the percutaneous catheter of FIG. 7 enteringthe patient's right carotid artery. Tissue debris, calcium plague,atheromatous material, or thrombi are often released downstream from thesurgical site, thereby making stroke the major post-operativecomplication in carotid endarterectomy. In use, catheter 1 is insertedpercutaneously into the carotid artery during endarterectomy, and filtermesh 30, mounted on the expansion framework, is positioned upstream thecarotid artery. After completion of the surgery, as described in Kaganovet al., U.S. application Ser. No. 08/759,591, filed Dec. 5, 1996,incorporated herein by reference, the flexible lines or wires are pulledto tightly contract the struts and filter mesh against the catheter sothat the entrapped embolic material would not be released downstream tocause cerebral infarction.

[0036] The length of the elongate instrument will generally be between 1and 20 inches, preferably approximately 12 inches. The length of eachstrut will generally be between 0.2 and 2 inches, preferablyapproximately 1 inch. The length of the flexible lines will generally bebetween 4 and 25 inches, preferably approximately 15 inches. The outerdiameter of the elongate instrument will generally be between 0.1 and0.5 inches, preferably approximately 0.25 inches. The foregoing rangesare set forth solely for the purpose of illustrating typical devicedimensions. The actual dimensions of a device constructed according tothe principles of the present invention may obviously vary outside ofthe listed ranges without departing from those basic principles.Moreover, it will be understood that the dimensions of a standardcannula are well known in the art and can be used in combination withthe framework disclosed herein.

[0037] Although the foregoing invention has, for purposes of clarity ofunderstanding, been described in some detail by way of illustration andexample, it will be obvious that certain changes and modifications maybe practiced which will still fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for treating a patient by open surgery,comprising the steps of: inserting a catheter into the patient through aperipheral artery, the catheter comprising an elongate member having aplurality of flexible lines and a plurality of struts arrangedcircumferentially around a distal region of the elongate member, eachstrut having an end that pivots away from the instrument, each flexibleline having a proximal end and a distal end that passes slideablythrough and beyond the end of the strut that carries it and is attachedto the strut immediately adjacent the strut that carries it; advancingthe catheter to a position downstream of a region of interest within anaorta; pushing the flexible lines distally to expand the struts radiallyoutward; performing an open surgical procedure on the aorta; pulling theflexible lines proximally to contract the struts radially inward; andremoving the catheter from the patient.
 2. The method of claim 1,wherein the catheter is inserted into the patient through an incision.3. The method of claim 1, wherein the catheter further comprises afilter mesh disposed over the struts and expandable by operation of theflexible lines, wherein during use the filter captures embolic material.4. The method of claim 1, further comprising the steps of performingcardiopulmonary bypass.
 5. The method of claim 1, further comprising thesteps of performing valve repair surgery.
 6. The method of claim 1,wherein one flexible line is carried by each strut, each flexible linehas a proximal end and a distal end that slideably engages the end ofthe strut that carries it, the distal end of each line is attached tothe strut immediately adjacent the strut that carries it, and each linepasses proximally beyond the first end of the strut that carries it. 7.The method of claim 1, wherein each strut comprises a tubular memberhaving a lumen and each flexible line is carried by the lumen of eachtubular strut.
 8. The method of claim 1, wherein the second end of eachstrut curves toward the immediately adjacent strut.
 9. The method ofclaim 1, wherein the flexible lines comprise pull wires.
 10. The methodof claim 1, wherein the catheter further comprises a balloon occluder.11. The method of claim 10, wherein the balloon occluder is mountedproximal the struts.
 12. The method of claim 1, wherein the flexiblelines are pushed distally until the operator is able to feel that theends of the struts have made contact with the endoluminal surface of theartery.
 13. The method of claim 1, wherein the catheter has a lumen thatextends between a proximal end and a distal end, and wherein the methodfurther comprises the step of infusing blood through the lumen.
 14. Amethod for treating a patient by open surgery, comprising the steps of:inserting a catheter into the patient through a peripheral artery, thecatheter comprising an elongate member having a plurality of flexiblelines and a plurality of struts arranged circumferentially around adistal region of the elongate member, each strut having an end thatpivots away from the instrument, each flexible line having a proximalend and a distal end that passes slideably through and beyond the end ofthe strut that carries it and is attached to the strut immediatelyadjacent the strut that carries it, the catheter further comprising afilter mesh disposed over the struts and expandable by operation of theflexible lines; advancing the catheter to a position downstream of aregion of interest within an aorta; pushing the flexible lines distallyto expand the struts radially outward; performing an open surgicalprocedure to access the aorta; blocking the aorta upstream of theexpanded filter; unblocking the aorta upstream of the expanded filter;pulling the flexible lines proximally to contract the struts radiallyinward; and removing the catheter from the patient.
 15. The method ofclaim 14, further comprising the steps of performing cardiopulmonarybypass.
 16. The method of claim 14, further comprising the steps ofperforming CABG.
 17. The method of claim 14, further comprising thesteps of performing valve repair surgery.
 18. The method of claim 14,wherein the step of blocking the aorta is performed by clamping theaorta.
 19. The method of claim 14, wherein the step of blocking theaorta is performed by balloon occlusion of the aorta.
 20. The method ofclaim 14, wherein the catheter further comprises a balloon occluder.